Disk Drive Servo Burst Phase-Shift Compensation
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Solution Overview
Problem
Existing disk drive servo systems face challenges in accurately positioning the transducing head due to phase errors introduced by the crescent-shaped transitions of servo bursts written on the disk, which can lead to incorrect position error signals and miscorrection of the head's position relative to the track center.
Innovation Solution
The solution involves writing the servo bursts, particularly the A and B bursts, slightly out of phase with the preamble to compensate for the shape-induced phase errors, ensuring that the signals remain coherent and accurate when sampled, thereby reducing errors in the position error signal and maintaining precise head positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If servo bursts are written with conventional phase alignment, then the servo pattern can be read, but phase errors are introduced due to crescent-shaped transitions causing incorrect position error signals
Solution Approach 1:
The patent applies preliminary anti-action by pre-shifting the phase of servo bursts (particularly A and B bursts) relative to the preamble before writing them to the disk. This pre-phase-shift counteracts the phase errors that will be introduced by the crescent-shaped transitions during reading, thereby compensating for the harmful effect before it occurs and maintaining accurate position error signals.
Solution Approach 2:
The patent changes the phase parameter of the servo bursts relative to the preamble. Specifically, the A and B bursts are written with a phase shift compared to the preamble phase, while the C and D bursts maintain a different phase relationship. This parameter change in phase alignment compensates for the distortion caused by crescent-shaped transitions and improves position error signal accuracy.
2Measurement precision
If phase shift compensation is applied to servo bursts, then position error signal accuracy improves, but the complexity of the servo pattern increases
Solution Approach 1:
The patent applies local quality by applying different phase relationships to different servo bursts within the same servo wedge. Specifically, the A and B bursts have one phase relationship with the preamble, while the C and D bursts have a different phase relationship. This localized differentiation allows phase error compensation without requiring complete redesign of the entire servo pattern, thus managing complexity.
Data Source
AI summary
A media includes a plurality of tracks, a preamble portion including a set of signals, a first servo burst having a first plurality of signals written substantially in phase with the preamble portion, and a second servo burst written out of phase with the preamble and the first servo portion. The media may be housed within a disk drive that includes a transducing head to read information from the media, and a read channel to read information from the disk including the information associated with the first servo burst and the second servo burst.